Internet Architecture Board / Internet Research Task Force Workshop on 
Congestion Control for Interactive Real-Time Communication
Vancouver, Canada, 2012


Impact of TCP on Interactive Real-Time Communication

Ilpo Järvinen, Binoy Chemmagate, Laila Daniel, Aaron Yi Ding, Markku Kojo - Uni Helsinki
Markus Isomäki - Nokia


Abstract:
Providing acceptable quality level for media flows
such as interactive video or audio is challenging in the presence
of TCP. Volatile TCP traffic such as Web traffic causes transient
queues to appear and vanish rapidly introducing jitter to the
packets of the media flow. Meanwhile long-lived TCP connections
cause standing queues to form. To get insights into this problem
space we conducted experiments in a real high-speed cellular
network. Our results confirm the existence of issues with both
Web traffic and long-lived TCP connections and highlight that
the use of parallel connections in Web browsers has high cost on
media flows. In addition, the recent proposal to increase initial
window of TCP to ten segments, if deployed, is going to make
the jitter problem even worse.